This invention relates to integrated circuits which employ optical inputs to the integrated circuit die as well as one or more electrical inputs or outputs.
Broadly speaking, the invention provides an interface layout for interfacing electrical and optical input signals to the integrated circuit die, wherein the electrical and optical input cells are arranged in one or more arrays, at least one array including at least one electrical input and at least one optical input.
The term xe2x80x9copticalxe2x80x9d is used herein broadly, and is not limited only to visible light. The term is intended to cover any radiation which obeys substantially the laws of optics.
The or each array may be linear (e.g. rows and/or columns), or multi-linear or non-linear, or the arrays may includes both linear and non-linear arrays.
One or more of the arrays may be at, or adjacent to, the periphery of the integrated circuit die. Alternatively, or additionally, the die may incorporate a xe2x80x9cfull areaxe2x80x9d input/output array in which the array is spread over substantially the entire area of the die (or at least a significant portion of the full area).
By arranging the optical and electrical inputs in the above manner, the integrated circuit designer can follow standard design practice, without having to pay extra consideration as whether the input cell is an optical cell or an electrical input cell.
Preferably, the optical input cell and the electrical input cell have generally equivalent xe2x80x9cgeographiesxe2x80x9d. For example, the optical input cell may include a photosensitive region which is positioned at an equivalent position to the electrically conductive input pad of the electrical input cell. Additionally, or alternatively, the optical input cell may include an input (processing) circuit which is positioned at an equivalent position to the electrical input circuit of an electrical input cell.
Preferably, an (or at least one) optical input cell occupies approximately the same size of die area as an electrical input cell (or at least one of the electrical input cells if the electrical input cells have a range of different sizes). Typically, the pad size for an electrical contact wire is about 100xc3x97100 xcexcm (although depending on the type of semiconductor substrate and the integration technology, this could be as small as about 50xc3x9750 xcexcm. Preferably, an optical input cell includes a photosensitive region of about the same size as a pad for the electrical input (or for at least one of the electrical inputs).
Preferably, the optical input cell includes conditioning circuitry which occupies approximately the same size area of die as does the input protection/buffer circuitry associated with an electrical input (or at least one of the electrical inputs).
Preferably, the or each optical input enters the integrated circuit package from or through the side of the package.